Abnormalities in central nervous system serotonergic functioning are highly correlated with impulsive behavior in patients with mood and personality disorders. Family and twin studies point to the heritability of a possible genetic defect in serotonergic functioning in individuals with high degrees of impulsive behavior. Preliminary studies have suggested that polymorphism of the locus for tryptophan hydroxylase (TPH, the rate limiting enzyme of serotonin synthesis in the CNS) may be useful in studying the genetic basic for abnormal serotonergic functioning. The purpose of this pilot study is to investigate whether specific TPH genotypes are related to an increased risk of impulsive behavior in patients with mood and personality disorders. In this study, samples of DNA will be obtained from ninety (90) patients with depression and personality disorders as well as each patient's parents (siblings if both parents are not available). These samples will undergo a specialized technique - polymerase chain reaction (PCR) - to clone multiple copies of the TPH gene. Using this technique, the TPH genotype for each individual (LL, UL, or UU) can be determined.